The present invention relates to an optical information processing apparatus, and more specifically, relates to an information recording/reproducing apparatus and a method such as an optical disk.
Up to the present practical use stage since the basic recording/reproducing system has been proposed, in the conventional optical disk, data are recorded in a time sequential mode on the concentric track thereof along the circumferential direction, which is similar to the conventional magnetic recording apparatus with utilizing magnetic force. The intervals of the adjoining tracks are set in order that data interference (referred to as a "crosstalk") among the respective tracks may be eliminated and thus no correlation of the data is present between the adjoining tracks.
There are conventional techniques for increasing the recording densities of the optical disks as described in, for instance, JP-A-2-53223.
Higher recording densities are continuously required for the information recording/reproducing apparatuses. To this end, in accordance with the conventional magnetic recording systems, the track intervals and the bit densities in the circumferential direction have been separately improved, whereby the recording plane densities could be increased. Similarly, a similar improving approach has been taken in the optical disk.
Since the resolution in the circumferential direction and the radial direction with respect to the conventional magnetic heads is asymmetrical with each other, there is a considerable difference between the track density and the bit density, e.g., approximately 10 times difference therebetween. However, since the spots used for the data recording/reproducing operations represent a isotropic characteristic in the optical disk, the track density is substantially equal to the line density. Nevertheless, even when the shape of the light spot are isotropically made small in order to increase the densities, although the line density may be improved, the track intervals could not be improved, as compared with the improvement in the line density. This is because there are many factors of the spot positional variations along the radial direction. As a result, the amount of variations becomes large and it is difficult to narrow the track intervals.